Expansion breakout board

I am collating a wishlist for the "basic" breakout for the expansion header that will simply enable plugging in of external drivers. This will allow people to use drivers such as the THB6064 drivers, MSD752 or similar, pololu drivers, legacy Duex4 (this breakout board will not be required for a Duex5) and anything else that can be added without adding significantly to the cost.

outputs (in order of perceived priority)

5 sets of 2x5 IDC headers for massmind and other PMinMO header compatible drivers. Signals would be at 5V

5 sets of Pololu headers (5V)

5 thermistor channels

50 pin Expansion for legacy Duex4 via ribbon cable

I would also add a I2C I/O expander as suggested in the prevous thread, + jumpers/dipswitch as required to allow the firmware to be aware of what is plugged in.

Anything else? (keeping in mind this is supposed to be a breakout board, not a fully featured expansion board!)

For those who use other vendor standard driver like Pololu, how would this people have heater channels ?

Are you planning to have the unused pins/signals from the 50-pin expansion header on a adapter board expansion header for
further purpose ?
(even if this are just routed to an unpopuleted expansion header place)